In recent years, there has been a substantial increase in the use of mobile communication devices for voice telephone services among mobile professionals and throughout the more general consumer population. In addition to providing voice telephone service, many mobile communication devices provide additional capabilities, such as email or text messaging services and even multimedia services. There are a variety of approaches that designers of mobile communication devices with multi-function capabilities provide for a user to input data into the mobile communication device in order to dial a phone number, create e-mail and text messages, and use other multimedia services. As mobile communication devices become increasing smaller, one approach is to use a reduced keypad, such as a telephone keypad, for dialing phone numbers, creating email and text messages, and using multimedia services. In this approach, the telephone keypad includes a fewer keys than letters in the alphabet, and each of the keys corresponds to a multiple characters. Various known methods have been developed for entering and displaying desired text using such types of reduced keypads. However, as the features of mobile device become more complex, a reduced keypad often becomes a limiting factor in accommodating and supporting all of the available features on the mobile communication device. In addition, although reduced keypads of the type described above have been developed, users of mobile communication devices tend to find it more comfortable and efficient to enter text when creating e-mail and text messages using a complete text keyboard.
Another method of providing multi-function capability is to provide a mobile communication device with a complete text keyboard, such as one having a standard QWERTY layout familiar to typists. In this approach, the QWERTY keyboard is provided on the face of the device and includes a complete set of alphanumeric keys and provides functions of dialing phone numbers, creating e-mail and text messages, and using multimedia services. However, as the demand for smaller mobile communication devices increases, the complete text keyboard has become a limiting factor in meeting this demand.
In an effort to satisfy the demand for miniature mobile communication devices that provide full voice and data communication capabilities while also retaining comfort and efficiency of entering text with complete keyboards, there have been developed mobile communication devices that include a telephone keypad on the face of the device and a complete text keyboard concealed behind a portion of the mobile communication device. Typically, these types of mobile communication devices have a body that includes at least a first housing and a second housing that is movably connected to the first housing. The second housing is capable of moving from a closed physical state relative to the first housing to an open physical state relative to the first housing. When the device is “closed” in such a manner, the complete text keyboard is concealed; whereas when the device is “open,” the complete text keyboard is exposed. In the closed physical state, the mobile communication device operates in a first mode of operation, which is typically a telephone call (i.e., voice) mode, and the telephone keypad on the face of the device is used to dial phone numbers. During the closed physical state, the complete text keyboard is hidden from the view of the user. When the mobile communication device is used in a second mode of operation, such as to create and send an e-mail message or text message, or for accessing multimedia services (i.e., data mode), the housing is moved to the open physical state thereby exposing the concealed complete text keyboard. The complete text keyboard can be used to enter text for the e-mail or text message, or for use with multimedia services. Example of the types of mobile communication devices that have a telephone keypad on the face of the device and a complete text keyboard concealed behind a portion of the mobile communication device include slider-type devices, flip-type devices, and folder-type devices.
Typically, manufactures of mobile communication devices design the devices to perform optimally in their first mode of operation, which is typically the voice mode, since wireless communication carriers and industry standards, such as CTIA, test the device for this mode of operation. In order to provide optimal performance, the antenna in the mobile communication device is tuned to provide maximum total radiated power in the first mode of operation. One method of tuning an antenna is to provide an impedance matching circuit between the antenna and the communication circuit in order to set the input impedance of the communication circuit equal to the impedance of the antenna.
The mobile communications device may include a variety of states that affect the performance of the antenna, such as, for example, the physical state of the device, the positional state of the device, or the operational state of the device. With regard to the physical state of the device, as explained above, the device may be used in a closed state for certain modes of operation and an open state for other modes of operation. For example, as explained above, slider-type, flip-type, and folder type devices typically operate in the first mode of operation when the second housing is positioned so as to conceal the complete text keyboard which is on the first housing (i.e., closed physical state). When the mobile device is to be used in its second mode of operation, such as for creating and sending e-mail or text messages, the second housing is moved relative to the first housing so as to expose the complete text keyboard (i.e., open physical state). When the second housing is moved to relative to the first housing for use in the second mode of operation, the performance of the antenna is degraded due to the antenna being detuned, as the antenna is optimized for performance when the device is in a closed physical state.
The positional state of the device may also affect the performance of the antenna. One type of positional state that can affect performance of the antenna is whether the device is in a hand-held position or a free-space position. For example, many mobile communication devices can be used in hand-held or handsfree modes of operation. Typically, when the device is being used in the hand-held mode of operation, the device is in the hand-held state such that it is being held by the user during operation. Conversely, when the device is being used in the handsfree mode of operation, the device is typically being used in the free-space state such that it does not need to be held by the user during operation. Many mobile communication devices are designed to provide optimal radiated power when the device is being used in one these positional states, such as for example, a hand-held position. Thus, when the device is being used in other positional states, such as free-space position, the antenna can become detuned and lead to a reduction in the total radiated power of the mobile communication device.
Operational states, such as whether the device is being used in voice mode or data mode, can also affect the radiated performance of the antenna. For example, many mobile devices are designed to perform optimally in certain modes of operation, such as voice mode. In order to provide optimal performance, the antenna in the mobile communication device is tuned to provide maximum total radiated power in these modes of operation. When the device is used in other modes of operation, such as data mode, the antenna may become detuned leading to reduced performance of the antenna. Reduced performance of the antenna reduces performance of the mobile device.
Since the antenna is a passive device, it cannot be tuned to multiple physical states, positional states, and operation states of the device based on the various conditions that may exist. Hence, there is a need to improve a mobile communication device's antenna radiated performance for multiple device states.